A boron powder is used in a combination with copper (Cu) powder in a conductive paste to form a copper electrode in order to reduce the Cu powder oxidation during firing in air. However the boron powder can be oxidized to flow out to cause glassy elution during firing as seen in FIG. 2. The elution could cause a defect such as breaking and open line in the copper electrode.
U.S. Pat. No. 8,129,088 discloses an air firing type of electrode that is formed with a photosensitive paste containing a copper powder, a boron powder, a glass frit, a photopolymerization initiator, photopolymerizable monomer, and organic medium.